The present invention relates generally to vehicle braking devices and more particularly to a warning mechanism for detecting wear in the brake shoe of a vehicle wheel braking assembly. The invention relates to a type of warning mechanism wherein a defaceable electrical circuit element such as a conductor wire is arranged to trigger a warning signal when depletion of the frictional brake shoe material has progressed beyond a predetermined limit.
In certain brake shoe wear warning devices of the type to which the present invention relates, a detection element for detecting the condition of wear of the brake frictional material in a brake assembly is provided behind the frictional material so that when wear of the friction material advances beyond a predetermined working limit, the warning device is electrically triggered to generate a signal notifying the occurrence of such excess wear. As a result, notification of the need to replace the brake friction material is acquired thereby preventing further deterioration of the brake performance, generation of undesirable braking noises and abnormal frictional heat.
In accordance with such known devices, however, the detection element is integrally incorporated in the brake friction material and cannot be readily separated therefrom. Accordingly, when trouble arises in the detection element, as for example would occur when the detection element malfunctions and produces a signal prematurely without the required amount of wear having occurred, it becomes necessary to replace extensive portions of the assembly including the frictional material and the detection element. Similarly, if problems should arise with regard to the brake friction material such as noise generation or improper braking effects, it again becomes necessary to replace both the brake friction material and the detection element even though only one of them may require replacement.
Moreover, when the wiring which is connected to the detection element becomes damaged, the brake friction material which is working normally must also be replaced together with the detection element. It will be apparent that the foregoing factors create disadvantages involving uneconomical utilization of braking elements.
The present invention is intended to overcome these problems by providing a warning mechanism having a detection element which is effective to indicate excessive brake shoe wear and which may be detachably mounted upon the brake shoe in cooperative engagement with the brake shoe friction material.